Geosteering is a process used to manage the trajectory of a borehole based on geological information gathered during a drilling operation, and a goal may be to reach specific geological targets. With some geosteering operations, a well plan with an expected well path is developed, and while a borehole is being drilled according to the well plan, geological information is gathered so that the well plan can be revised as necessary to reach a desired geological target. The geological information may be gathered, for example, using mud logging, measurement while drilling (MWD), or logging while drilling (LWD).
Some conventional geosteering approaches rely on a geosteering structure model based on gamma ray (GR) or resistivity logs. In the case of a GR log model, the model may be initialized with flat layers with constant GR values, e.g., based on measurements taken from a pilot well GR log. Then, during drilling of the horizontal part of a wellbore, real time information, such as a measured GR log and real time formation telemetry data measurements, are collected from the well drilling tool.
As drilling progresses, geosteering software allows an operator to visualize differences between the structure model and the observed data, e.g., by comparing a synthetic GR log that is calculated from the structure model and the known well trajectory and current position, and a measured GR log calculated from the real time measurements. Based upon these differences, an operator may be permitted to manually modify the structure model to better match the synthetic and measured GR logs. Accordingly, geosteering can be a highly involved process and can be highly dependent upon the expertise and experience of the operator.